(a) Field of the Invention
The present invention relates to a signaling method for direct communication between terminals.
(b) Description of the Related Art
Direct communication refers to signal transmission and reception between terminals without mediation with a base station or control therebetween. As demand for direct communication between terminals is on the rise, a direct communication method within or outside an infrastructure communication region is required.
Standards for direct communication between terminals include IEEE Std. 802.16.1a. The IEEE Std. 802.16.1a is a standard that allows for direct communication between terminals as resources dedicated for direct communication are allocated in time and frequency domains in a frame structure of infrastructure communication between a base station and a terminal, and signals are exchanged between terminals through allocated radio resources.
To provide different QoS for each traffic stream in a radio resource region, flows are established at a MAC layer, and a MAC PDU (packet data unit) is constructed for each flow. In talk-around direct communication (TDC) according to IEEE Std. 802.16.1a, flow IDs (FIDs) are established in a unidirectional link establishment process, and the transmitting side configures the FIDs to not overlap. However, if the direction of unidirectional traffic is changed by a token handover procedure, the traffic source may be changed to a terminal with no FID. In this case, the transmitting terminal is not able to construct a MAC PDU for the terminal with no FID.
A multicast connection involves transmitting data to a plurality of user groups. A connection setup procedure is performed in the step of setting up an initial multicast connection, by which a multicast connection group is created. However, the existing IEEE Std. 802.16.1a does not provide for an operation scenario for a user (terminal) who leaves the multicast connection group. Also, this standard does not define a procedure of transmitting multicast connection setup information after the setup step, and therefore additional users who want to participate in the multicast connection group may not be able to participate in the multicast connection group.
The IEEE Std. 802.16.1a does not define a procedure of detecting the presence or absence of a receiving terminal within a communication distance when making a unidirectional unicast and multicast connection, or releasing a connection that fails to connect to a communication channel.